1. Field of the Invention
The present invention relates to a gel-forming silicone composition, and more particularly to a silicone composition which, when heated to a relatively low temperature, is able to form a gel cured product (namely, is curable to be a silicone gel) having good adhesion to electronic component parts and the like.
2. Description of the Prior Art
Heretofore, silicone gels have been used for protection of electronic devices such as hybrid ICs, etc. A silicone gel for this use is required to have good adhesion to electronic parts and the like, in order to protect the electronic parts against water and so on.
As a material for forming silicone gel, there have been known a variety of addition-curing type organopolysiloxane compositions (See Japanese Pre-examination Patent Publication (KOKAI) Nos. 56-143241, 62-39659, 635655 and 63-33475.).
However, gel cured products obtained from the above-described compositions have the drawback of low adhesive properties and, hence, poor adherence to substrates. That is, where such a composition is used for potting an electronic part, the resulting gel cured product may separate from the electronic part to generate a gap therebetween, allowing moisture, water or the like to come in through the gap to cause corrosion, insulation failure or the like.
On the other hand, there are known a number of techniques for obtaining an elastomer having good adhesive properties by use of an adhesion promotor. The adhesion promotors used in these techniques include an organopolysiloxane containing a silicon-bonded hydrogen atom and a trialkoxysilyl group (See Japanese Pre-examination Patent Publication (KOKAI) No. 48-16592), an organopolysiloxane containing a silicon-bonded hydrogen atom as well as an ester group and/or a glycidyl group (See Japanese Pre-examination Patent Publication (KOKAI) No. 50-39345), a reaction product of an aminoalkylalkoxysilane and a glycidoxyalkylalkoxysilane (See Japanese Patent Publication (KOKOKU) Nos. 52-8854 and 55-41702), and so on. These techniques, however, have the disadvantage that adhesion cannot be developed in a short time or that a satisfactory adhesion cannot be obtained at room temperature or by heating to a slightly raised temperature. Besides, the conventional techniques using an adhesion promotor as above are primarily for compositions which form a highly elastic cured product (elastomer), and the cured product is quite different from a gel cured product. For instance, where such an elastomer is used as a protecting or insulating material for semiconductor circuit components or the like, thermal stress will be generated in the elastomer itself due to heat generation by the circuit components, environmental temperature conditions, etc., resulting in breakage of the semiconductor device. Moreover, where the technique is applied to a gel-forming composition, it is difficult to prepare a composition having low crosslink degree, which is an intrinsic property of gels.